Adsorption of acid dye onto activated carbons prepared from agricultural waste bagasse by ZnCl2 activation

Fabrication of spirulina based activated carbons for wastewater treatment

The lack of safe drinking water is among the main problems to be faced by many areas of the world due to climate change, unrestrained population increases, and unsustainable usage of water sources. Therefore, research projects focusing on water quality, pollution, and control for sustainable water sources are in high demand to manage any unexpected changes in water sources. Drinking water sources may be contaminated with organic and inorganic chemicals, disinfection by-products, and microorganisms. Different treatment processes to remove these contaminants from water may be limited because of their high costs and time-consuming or require a multiple-barrier approach to improving performance. Therefore, there is a great need to develop an effective process for removing impurities. The primary objective of this study is to assess the effectiveness of algae-based activated carbons and develop a unique, low-cost sustainable process for wastewater treatment. Activated carbons were produced from pelletised algae powder using carbonisation and chemical activation. Chemical activation was carried out with calcium chloride (CaCl2) and zinc chloride (ZnCl2) as chemical agents. Furthermore, Brunauer-Emmett-Teller (BET) along with scanning electron microscopy (SEM) techniques were used to analyse the morphology, surface area, as well as the porosity of the prepared activated carbons to build a water column filter. Based on the results, algae-based carbon with CaCl2 activation provided a better surface area (197.7486 m2/g) and cumulative pore volume (0.105284 cm3/g). The filtration process using algae-based activated carbon can be a promising technique for water treatment with some further improvement and modifications.

Cost-effective removal of toxic methylene blue dye from textile effluents by new integrated crosslinked chitosan/aspartic acid hydrogels

Chitosan/aspartic acid hydrogels were synthesized for MB dye removal from textile aqueous effluents with different ratios by gelation of chitosan with non-toxic gelling agent, crosslinker, glutaraldehyde (Glu). The obtained hydrogels were characterized by spectral and morphological techniques. The characterization techniques confirmed successful preparations and MB dye adsorption. Batch experiments were done to investigate the effects of adsorbent dose, pH, contact time, temperature, and initial MB dye concentration. The optimum conditions were: adsorbent dose 0.1 g, pH 5, contact time 30 min, and temperature 25 °C for Chitosan-Aspartic Acid Hydrogel 1 (CSAA-HG1) and adsorbent dose 0.4 g, pH 2, contact time 60 min, temperature 25 °C for Chitosan-Aspartic Acid Hydrogel 2 (CSAA-HG2). Adsorption capacity of newly hydrogels CSAA-HG1,2 was compared with each other. Adsorption efficiencies reached 99.85 % for CSAA-HG1 and 99.88 % for CSAA-HG2. MB dye adsorption on CSAA-HG1,2 followed Freundlich isotherm model (R2 = 0.94 and 0.92, respectively). Both adsorbents exhibited pseudo-second-order kinetics for MB dye adsorption (R2 = 1). The negative ΔHo indicated that the MB dye adsorption was exothermic, negative ΔGo confirmed that MB dye adsorption process was spontaneous and low values of ∆So indicated low degree of freedom, ordered MB dye molecules on CSAA-HG1,2 surfaces.

Synthesis and Characterization of Orange Peel Modified Hydrogels as Efficient Adsorbents for Methylene Blue (MB)

In recent years, due to the developments in the textile industry, water contaminated with synthetic dyes such as methylene blue (MB) has become an environmental threat based on the possible impacts in terms of chemical and biochemical demand, which leads to disturbance in aquatic plants photosynthesis, besides their possible toxicity and carcinogenicity for humans. In this work, an adsorbent hydrogel is prepared via free radical polymerization comprising acrylic acid (PAA) as a monomer and orange peel (OP) as a natural modifier rich in OH and COOH present in its cellulose and pectin content. The resulting hydrogels were optimized in terms of the content of OP and the number of cross-linkers and characterized morphologically using Scanning electron microscopy. Furthermore, BET analysis was used to follow the variation in the porosity and in terms of the surface area of the modified hydrogel. The adsorption behavior was found to follow pseudo-second-order as a kinetic model, and Langmuir, Freundlich, and Temkin isotherm models. The combination of OP and PAA has sharply enhanced the adsorption percent of the hydrogel to reach 84% at the first 10 min of incubation with an adsorption capacity of more than 1.93 gm/gm. Due to its low value of pHPZc, the desorption of MB was efficiently performed at pH 2 using HCl, and the desorbed OP-PAA were found to be reusable up to ten times without a decrease in their efficiency. Accordingly, OP-PAA hydrogel represents a promising efficient, cost-effective, and environmentally friendly adsorbent for MB as a model cationic dye that can be applied for the treatment of contaminated waters.

Activated carbon prepared by co-pyrolysis of waste tobacco straw and waste LDPE mulch film: characterization and application for methylene blue removal

Efficient and inexpensive sorbents play a key role in removing organic pollutants from water bodies. In this study, a series of high surface area activated carbons (ACs) with excellent adsorption performance was prepared by co-pyrolysis of the waste tobacco straw and the waste low-density polyethylene (LDPE) mulch film. Using the maximum adsorption capacity of methylene blue (MB) as an indicator, the variables such as LDPE content, K₂CO₃ to raw material ratio, activation time, and activation temperature were optimized. The optimal synthesis conditions were as follows: LDPE content of 40%, K₂CO₃/raw material ratio of 1 : 2, activation temperature of 900 °C, and activation time of 100 min. The maximum adsorption capacity of MB was up to 849.91 mg g^-1. The results of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), and BET showed that the moderate addition of LDPE was beneficial to the pyrolysis of the waste tobacco straw, bringing about the enrichment of surface groups (-OH, -COOH) and increasing its specific surface area and pore volume (up to 1566.7 m² g^-1 and 0.996 cm³ g^-1, respectively). The equilibrium data of MB adsorption by the composite activated carbon (PAC) was consistent with the Langmuir isotherm, while the adsorption kinetics were better described by a pseudo-second-order kinetic model. This work reveals the feasibility of LDPE mulch film and waste tobacco straw as potential and inexpensive precursors for preparing high surface area AC adsorbents.

Recent Advanced Supercapacitor: A Review of Storage Mechanisms, Electrode Materials, Modification, and Perspectives

In recent years, the development of energy storage devices has received much attention due to the increasing demand for renewable energy. Supercapacitors (SCs) have attracted considerable attention among various energy storage devices due to their high specific capacity, high power density, long cycle life, economic efficiency, environmental friendliness, high safety, and fast charge/discharge rates. SCs are devices that can store large amounts of electrical energy and release it quickly, making them ideal for use in a wide range of applications. They are often used in conjunction with batteries to provide a power boost when needed and can also be used as a standalone power source. They can be used in various potential applications, such as portable equipment, smart electronic systems, electric vehicles, and grid energy storage systems. There are a variety of materials that have been studied for use as SC electrodes, each with its advantages and limitations. The electrode material must have a high surface area to volume ratio to enable high energy storage densities. Additionally, the electrode material must be highly conductive to enable efficient charge transfer. Over the past several years, several novel materials have been developed which can be used to improve the capacitance of the SCs. This article reviews three types of SCs: electrochemical double-layer capacitors (EDLCs), pseudocapacitors, and hybrid supercapacitors, their respective development, energy storage mechanisms, and the latest research progress in material preparation and modification. In addition, it proposes potentially feasible solutions to the problems encountered during the development of supercapacitors and looks forward to the future development direction of SCs.

Nanolayer-Constructed TiO(OH)2 Microstructures for the Efficiently Selective Removal of Cationic Dyes via an Electrostatic Interaction and Adsorption Mechanism

Efficient removal of organic dyes from contaminated water has become a great challenge and urgent work due to increasingly serious environmental problems. Here, we have for the first time prepared nanolayer-constructed TiO(OH)₂ microstructures which can present negative charge by deprotonation of the hydroxyl group to efficiently and selectively remove cationic dyes from aqueous solution through electrostatic interaction and an attraction mechanism. The nanolayer-constructed TiO(OH)₂ microstructures achieve a high adsorption capacity of 257 mg g^-1 for methylene blue (MB). The adsorption kinetics, thermodynamics, and isotherms of MB over the TiO(OH)₂ microstructures have been studied systemically. The experimental measurements and corresponding analyses demonstrate that the adsorption process of MB on TiO(OH)₂ microstructures follows a kinetic model of pseudo-second-order adsorption, agrees well with the Langmuir isotherm mode, and is a spontaneous and exothermic physisorption. Fourier transform infrared (FT-IR) spectra confirm that the prepared TiO(OH)₂ microstructures possess hydroxyl group which can deprotonate to present negative charge in solution. Further experimental studies evidently demonstrate that the TiO(OH)₂ microstructures also can remove other cationic dyes with positive charge such as basic yellow 1, basic green 4, and crystal violet but cannot adsorb anionic dye of methyl orange (MO) with negative charge in aqueous solution. The measurements for FT-IR spectra and the adsorption of cationic and anionic dyes evidently reveal that the adsorption of cationic dyes over the TiO(OH)₂ microstructures is achieved by the electrostatic interaction and attraction between TiO(OH)₂ and the dye. This work opens a strategy for the design of new absorbents to efficiently remove organic dyes from aqueous solution through an electrostatic attraction-driven adsorption process.

Activated Sawdust-Based Adsorbent for the Removal of Basic Blue 3 and Methylene Green from Aqueous Media

Dye pollution is a serious threat to aquatic environment and human health. Although activated carbon is an efficient adsorbent for dye reclamation from effluents, its expressive nature renders its use on large commercial scales. On the other hand, waste biomasses are not effectively used for any beneficial purposes. Sawdust is a waste biomass of wood mills, and due to its small particle sizes, it has the potential to be used as adsorbent. In spite of its uses for cooking purposes, it is sometimes used as adsorbent as such or converted into activated carbon. In raw form, it is not a good adsorbent; however, its adsorption capacity can be increased by applying chemical modifications. In the present study, sawdust of paper mulberry (Broussonetia papyrifera) was used as adsorbent for the removal of basic blue 3 and methylene green from water after chemical modification with NaOH and HCl in 1 : 1. The prepared adsorbent was characterized by SEM and FTIR, whereas the surface area was estimated through an already reported method in literature. Batch experiments were performed to determine the isothermal and kinetic parameters of the selected dyes adsorption on activated sawdust. The effect of adsorbent dosage and temperature on adsorption were also evaluated. The best fit of the kinetic data was achieved with pseudosecond-order model for which $R^2$ values were approximately equal to 1 whereas Langmuir model was most suitable model to explain the isothermal data. The optimum adsorbent dosage was 0.05 g for both of the selected dyes. Different thermodynamic parameters, such as enthalpy ( $∆H=18.5$ and 8.334 kJ/mol respectively for basic blue 3 and methylene green), entropy ( $∆S^{°}=62.41$ and 29.22 kJ/molK respectively for basic blue 3 and methylene green), and Gibbs free energy ( $∆G^{°}=-83.6$ , -410, and -1658 kJ/mol (basic blue)/-65, -519, and -1139 kJ/mol (methylene green), were estimated, and the process was found to be endothermic, spontaneous, and feasible. The increase in $\Delta G^{°}$ with increase in temperature indicates that the adsorption process is favorable at high temperature. The prepared adsorbent could be effectively used in the reclamation of water loaded with other contaminants; however, further experiments are needed to increase the adsorption capacity of the adsorbent.

Advanced Material-oriented Biomass Precise Reconstruction: A Review on Porous Carbon with Inherited Natural Structure and Created Artificial Structure by Post-treatment

Manufacturing of porous carbon with biomass resources has been intensively investigated in recent decades. The diversity of biomass species and great variety of processing methods enable the structural richness of porous carbon as well as their wide applications. In this review, we specifically focused on the structure of biomass-derived porous carbon either inherited from natural biomass or created by post-treatment. The intrinsic structure of plant biomass was briefly introduced and the utilization of the unique structures at different length-scales were discussed. In term of post-treatment, the structural features of activated carbon by traditional physical and chemical activation were summarized and compared in a wide spectrum of biomass species, statistical analysis were performed to evaluate the effectiveness of different activation methods in creating specific pore structures. The similar pore structure of biomass-derived carbon and coal-derived carbon suggested a promising replacement with more sustainable biomass resources in producing porous carbon. In summary, using biomass as porous carbon precursor endows the flexibility of using its naturally patterned micro-structure and the tunability of controlled pore-creation by post treatment. This article is protected by copyright. All rights reserved.

Adsorption of Cationic Dyes on a Magnetic 3D Spongin Scaffold with Nano-Sized Fe3O4 Cores

The renewable, proteinaceous, marine biopolymer spongin is yet the focus of modern research. The preparation of a magnetic three-dimensional (3D) spongin scaffold with nano-sized Fe3O4 cores is reported here for the first time. The formation of this magnetic spongin-Fe3O4 composite was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA) (TGA-DTA), vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FTIR), and zeta potential analyses. Field emission scanning electron microscopy (FE-SEM) confirmed the formation of well-dispersed spherical nanoparticles tightly bound to the spongin scaffold. The magnetic spongin-Fe3O4 composite showed significant removal efficiency for two cationic dyes (i.e., crystal violet (CV) and methylene blue (MB)). Adsorption experiments revealed that the prepared material is a fast, high-capacity (77 mg/g), yet selective adsorbent for MB. This behavior was attributed to the creation of strong electrostatic interactions between the spongin-Fe3O4 and MB or CV, which was reflected by adsorption mechanism evaluations. The adsorption of MB and CV was found to be a function of pH, with maximum removal performance being observed over a wide pH range (pH = 5.5-11). In this work, we combined Fe3O4 nanoparticles and spongin scaffold properties into one unique composite, named magnetic spongin scaffold, in our attempt to create a sustainable absorbent for organic wastewater treatment. The appropriative mechanism of adsorption of the cationic dyes on a magnetic 3D spongin scaffold is proposed. Removal of organic dyes and other contaminants is essential to ensure healthy water and prevent various diseases. On the other hand, in many cases, dyes are used as models to demonstrate the adsorption properties of nanostructures. Due to the good absorption properties of magnetic spongin, it can be proposed as a green and uncomplicated adsorbent for the removal of different organic contaminants and, furthermore, as a carrier in drug delivery applications.

Evaluation of tire derived rubber (TDR) fixed biofilm reactor (FBR) for remediation of Methylene blue dye from wastewater

The present investigation is focused on development of aerobic biofilm on tire-derived rubber (TDR) media and then evaluation of such system for bioremediation of Methylene blue (MB) dye for 9 weeks. After 9 weeks of operation, the COD, BOD, ammonia and color values have been declined by 89.2%, 98.3%, 99.61% and 99.81%, respectively, While SEM-EDX results showed a variance in weight percent of various elements in TDR without biofilm i.e. raw TDR media, as well as in the 1st and 9th-week samples. Moreover, fine and strong peaks were observed in both the MB simulated wastewater and 9th week TDR samples at 1190, 1300, 1400, 1450, 1500 and 1618 cm^-1 respectively by Raman Spectroscopic analysis. Further, FTIR analysis was performed for the MB simulated wastewater, and absorbance peaks ranging from 1591 to 1363 cm^-1 and 3410 cm^-1 were observed in all the samples with different intensities. To assess the biodeterioration of the TDR media, ATR was performed for the raw, 1st, 2nd and 9th week TDR media samples and in the raw TDR, two important bands, 842 and 2962 cm^-1 were noticed representing -CH = CH and -CH₃. A clear variation of bands and peak intensities were observed in different support media samples. The results indicate that TDR media is a resilient, chemically resistant material and could be employed for the biofilm growth for biological treatment of textile dye wastewater.

Studies of the potential of a native natural biosorbent for the elimination of an anionic textile dye Cibacron Blue in aqueous solution

This work is devoted to the adsorption of Cibacron Blue (CB) an anionic textile dye, on bean peel (BP) an agricultural waste with neither activation nor carbonization. The adsorption was realized in batch configuration at ambient temperature in acidic medium. The adsorbent was characterized by FTIR, SEM and BET analyses; the equilibrium isotherms and kinetics were also studied. It has been found that this waste could be used as a low-cost biosorbent for CB elimination under optimal working conditions. The rate of CB elimination reaches 95% on bean bark (3.6 g/L) at pH 2.2 and a reject concentration of 25 mg/L. The pseudo-second-order describes suitably the experimental data and the external diffusion is the rate-determining step. The Freundlich isotherm fits better the CB adsorption with a correlation coefficient (R²) of 0.94 and an RMSE = 1.5115. The negative enthalpy (ΔH) and free enthalpy (ΔG°) indicate a physical and spontaneous nature of the CB biosorption onto the biomaterial.

Adsorption of Malachite Green Dye onto Mesoporous Natural Inorganic Clays: Their Equilibrium Isotherm and Kinetics Studies

Contamination of water with organic dyes is a major environmental concern as it causes serious life-threatening environmental problems. The present research was designed to evaluate the potential of three different natural inorganic clays (NICs) i.e., Pakistani bentonite clay (PB), bentonite purchased from Alfa Aesar (BT), and Turkish red mud (RM) for malachite green (MG) dye removal from an aqueous solution. Various analytical techniques, namely X-ray fluorescence spectrometry (XRF), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller surface area measurement (BET), and thermogravimetric analysis (TGA), were used to investigate the physicochemical properties of the NICs samples. The effect of adsorption operational parameters such as contact time, aqueous phase pH, dye concentration, and amount of NICs on the adsorption behavior of MG onto NICs samples were investigated under the batch adsorption system. The equilibrium and kinetic inspection reflected the best description of MG adsorption behavior by the Langmuir isotherm model and pseudo-first-order kinetic model, respectively. The results indicated that the adsorption was favorable at higher pH. The maximum adsorption capacities calculated by Langmuir isotherm for PB, BT, and RM were found to be 243.90 mg/g, 188.68 mg/g, and 172.41 mg/g, respectively. It can be concluded that natural inorganic clays with a higher surface area can be used as an effective adsorbent material to remove the MG dye from an aqueous solution.

Treatment of Yellow Phosphorus Slag and Reuse of It as an Absorbent of Chromium (VI) Ions and Methylene Blue

Yellow phosphorus is used widely in the world for production of phosphoric acid, various phosphates, flame retardant, detergent, water treatment, metal surface treatment, etc. After the production of yellow phosphorus, a large amount of phosphorus sludge is discharged to environment, causing environment pollution. This work focused on treatment of yellow phosphorus slag (YPS) and application of it as an absorbent for chromium (VI) ion and methylene blue. The YPS was first washed with water to remove phosphoferrite (FeP) and impurities and then being milled and transferred to a float sorting system to obtain YPS particles. The characteristics of YPS particles were determined by inductively coupled plasma-mass-spectrometry (ICP-MS), energy-dispersive X-ray spectroscopy (EDX), infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), zeta potential, and nitrogen adsorption methods. The YPS particles were retreated with NaOH, HNO3, and EDTA solutions to evaluate the influence of these agents on metal ion and organic compound adsorption ability by YPS. The adsorption parameters of chromium (VI) ion and methylene blue (MB) by treated YPS particles were recognized by the ultraviolet-visible (UV-Vis) spectrometer. The effects of temperature, pH solution, and initial concentration of absorbed substances on the adsorption ability were investigated. The adsorption isotherms and adsorption kinetics of chromium (VI) ion and MB by YPS particles were also determined. The obtained results confirmed that the green technology used to treat the YPS2 particles is suitable to obtain an effective absorbent. The adsorption efficiency of YPS2 particles for removal of chromium (VI) ions is smaller than that for removal of MB in aqueous solutions. The adsorption isotherm of MB adsorption process is complied with the Langmuir isotherm while the adsorption kinetic fits well with the pseudo-second-order reaction model. The thermodynamic parameters of MB adsorption processed on YPS2 were calculated and discussed.

Effective use of elderberry (Sambucus nigra) pomace in biosorption processes of Fe(III) ions

Elderberry (Sambucus nigra) pomace obtained as a result of processing in the food industry was examined for the bioremoval of Fe(III) ions from aqueous solutions in batch experiments. Several physicochemical properties of the biomass were analyzed using a variety of analytical methods, such as particle size distribution, elemental composition (SEM-EDS), X-ray diffraction analysis (XRD), thermogravimetry (TGA, DTG), specific surface area and average pore diameter (BET adsorption isotherms), volume of pores and pore volume distribution (BJH), morphology (SEM), mid-infrared analysis FT-IR. The impact of adsorbent dosage, initial concentration, pH and contact time on the process efficiency was studied. The calculated maximum adsorption efficiency and capacity was estimated at 99.5% and 33.25 mg/g, respectively. The biosorption kinetic analysis indicated that the removal process fits better to the pseudo-second order equation and the Langmuir model. Summing up, the biosorbent is a promising low-cost material for the highly effective iron recovery from effluents and improvement of water quality.

A Simple Approach for Determining the Maximum Sorption Capacity of Chlorpropham from Aqueous Solution onto Granular Activated Charcoal

UV-Vis spectrophotometer was used to determine chlorpropham (CIPC) concentration in aqueous solution. The method was validated in term of linearity, precision and limit of detection and limit of quantitation. The correlation coefficient of standards calibration curve of (1.0–10.0 µg/mL CIPC) was R2 = 1 with a precision (RSD%, n=10) ranged from (0.87–0.53%). The limit of detection (LOD) and limit of quantitation (LOQ) based on the regression statistics of the calibration curve data of (1.0–10.0 µg/mL CIPC) were 0.04 µg/mL and 0.11 µg/mL respectively. The activated carbon adsorbent was found to be effective for the removal approximately 80% of CIPC from aqueous solution. Several isotherm models (Langmuir, Freundlich, Tempkin and Dubinin–Radushkevich) were evaluated. The maximum monolayer sorption capacity (Qm) from the Langmuir isotherm model was determined to be (44316.92 µg/g). The separation factor (RL) is 0.11 which indicates a favorable equilibrium sorption with the R2 value of 0.99, indicating that the Langmuir isotherm model fit the experimental sorption data well.

A review on the applicability of activated carbon derived from plant biomass in adsorption of chromium, copper, and zinc from industrial wastewater

Metal ion contamination in wastewater is an issue of global concern. The conventional methods of heavy metal removal from wastewater have some drawbacks, ranging from generation of sludge to high cost of removal. Adsorption technique for copper(II), zinc(II), and chromium(VI) using activated carbon has been found efficient. However, it is not economical on a large scale. This, therefore, necessitates the search for economical and readily available plant biomass-based activated carbons for the sequestration of the metal ions. This review presents the state of the art on the adsorption of copper(II), zinc(II), and chromium(VI) from industrial wastewater. Based on the literature review presented, the groundnut husk and corncob based activated carbons were found to possess the maximum adsorption capacities for copper(II), zinc(II), and chromium(VI) removal, when compared with the other plant biomass-based activated carbons. The high values of the adsorption capacities obtained were as a result of the isotherms and pH of the adsorbent as well as the initial concentration of the metal solutions. From the review, the equilibrium data fitted better with Langmuir and Freundlich isotherms than with other isotherms. Research gaps were identified which include a need to investigate the kinetic and the thermodynamic behaviors of the metal ions onto the studied adsorbents. Furthermore, a comparative analysis of the three types of activation of the adsorbents should be investigated using single and multi-metals. The optimization of particle size, contact time, temperature, initial concentration, and adsorbent dosage for adsorption of copper(II), zinc(II), and chromium(VI) onto the studied adsorbents using response surface methodology is equally required.

Rational Design of Carbon Nanomaterials for Electrochemical Sodium Storage and Capture

Electrochemical sodium storage and capture are considered an attractive technology owing to the natural abundance, low cost, safety, and cleanness of sodium, and the higher efficiency of the electrochemical system compared to fossil-fuel-based counterparts. Considering that the sodium-ion chemistry often largely deviates from the lithium-based one despite the physical and chemical similarities, the architecture and chemical structure of electrode materials should be designed for highly efficient sodium storage and capture technologies. Here, the rational design in the structure and chemistry of carbon materials for sodium-ion batteries (SIBs), sodium-ion capacitors (SICs), and capacitive deionization (CDI) applications is comprehensively reviewed. Types and features of carbon materials are classified into ordered and disordered carbons as well as nanodimensional and nanoporous carbons, covering the effect of synthesis parameters on the carbon structure and chemistry. The sodium storage mechanism and performance of these carbon materials are correlated with the key structural/chemical factors, including the interlayer spacing, crystallite size, porous characteristics, micro/nanostructure, morphology, surface chemistry, heteroatom incorporation, and hybridization. Finally, perspectives on current impediment and future research directions into the development of practical SIBs, SICs, and CDI are also provided.

Effect of Activating Agent on the Properties of TiO₂/Activated Carbon Heterostructures for Solar Photocatalytic Degradation of Acetaminophen

Several activated carbons (ACs) were prepared by chemical activation of lignin with different activating agents (FeCl₃, ZnCl₂, H₃PO₄ and KOH) and used for synthesizing TiO₂/activated carbon heterostructures. These heterostructures were obtained by the combination of the activated carbons with a titania precursor using a solvothermal treatment. The synthesized materials were fully characterized (Wavelength-dispersive X-ray fluorescence (WDXRF), X-ray diffraction (XRD), Scanning electron microscopy (SEM), N2 adsorption-desorption, Fourier transform infrared (FTIR) and UV-visible diffuse reflectance spectra (UV-Vis DRS) and further used in the photodegradation of a target pharmaceutical compound (acetaminophen). All heterostructures were composed of anatase phase regardless of the activated carbon used, while the porous texture and surface chemistry depended on the chemical compound used to activate the lignin. Among all heterostructures studied, that obtained by FeCl₃-activation yielded complete conversion of acetaminophen after 6 h of reaction under solar-simulated irradiation, also showing high conversion after successive cycles. Although the reaction rate was lower than the observed with bare TiO₂, the heterostructure showed higher settling velocity, thus being considerably easier to recover from the reaction medium.

A Review on the Synthesis and Characterization of Biomass-Derived Carbons for Adsorption of Emerging Contaminants from Water

This review analyzes the preparation and characterization of biomass-derived carbons and their application as adsorbents of emerging contaminants from water. The study begins by identifying the different types of emerging contaminants more often found in water streams, including a brief reference to the available technologies for their removal. It also describes the biomass sources that could be used for the synthesis of biochars and activated carbons (AC). The characterization of the adsorbents and the different approaches that can be followed to learn about the adsorption processes are also detailed. Finally, the work reviews literature studies focused on the adsorption of emerging contaminants on biochars and activated carbons synthesized from biomass precursors.

Marine-Biomass-Derived Porous Carbon Sheets with a Tunable N-Doping Content for Superior Sodium-Ion Storage

Synthesis of the electrode materials of sodium-ion storage devices from sustainable precursors via green methods is highly desirable. In this work, we fabricated a unique N, O dual-doped biocarbon nanosheet with hierarchical porosity by direct pyrolysis of low-cost cuttlebones and simple air oxidation activation (AOA) technique. With prolonging AOA time, thickness of the carbon sheets could be reduced controllably (from 35 to 5 nm), which may lead to tunable preparation of carbon nanosheets with a certain thickness. Besides, an unexpected increase in N-doping amount from 7.5 to 13.9 atom % was observed after AOA, demonstrating the unique role of AOA in tuning the doped heteroatoms of carbon matrix. This was also the first example of increasing N-doping content in carbons by treatment in air. More importantly, by optimizing the thickness of carbon sheets and heteroatom doping via AOA, superior sodium capacity-cycling retention-rate capability combinations were achieved. Specifically, a current state-of-the-art Na⁺ storage capacity of 640 mAh g^-1 was obtained, which was comparable with the lithium-ion storage in carbon materials. Even after charging/discharging at large current densities (2 and 10 A g^-1) for 10 000 cycles, the as-obtained samples still retained the capacities of 270 and 138 mAh g^-1, respectively, with more than 90% retention. The assembled sodium-ion capacitors also delivered a high integrated energy-power density (36 kW h kg^-1 at an ultrahigh power density of 53 000 W kg^-1) and good cycling stability (90.5% of capacitance retention after 8000 cycles at 5 A g^-1).

Prickly pear cactus cladodes powder of Opuntia ficus indica as a cost effective biosorbent for dyes removal from aqueous solutions

The textiles manufacturing is one of the core industries that release a huge amount of dyes during the dyeing process. As a result, the growing demand of an efficient and low-cost treatment has given rise to alternative adsorbents. In the present study, prickly pear cactus cladodes powder (PPCP) of Opuntia ficus indica was investigated as an ecofriendly and low-cost biosorbent of Acid orange 51 (AO51) and Reactive Red 75 (RR75) dyes commonly used in dyeing. The FTIR spectroscopic characterization of PPCP showed the heterogeneity in surface structure and functional groups which confers to the biosorbent its capability to interact with acidic (AO51) and reactive (RR75) dyes molecules. Effects of pH, temperature, initial dye concentration and adsorbent dose on adsorption yield were investigated. The dyes uptake process was closely fitted to the pseudo-second order kinetic for both dyes. Experimental data were analyzed by applying the Langmuir, Freundlich, Dubinin-Raduskevich, Temkin, Redlich-Peterson, and BET isotherms equations. The models of BET and Langmuir were considered as the best isotherms models fitting experimental data, respectively, of RR75 and AO51. The maximum Langmuir monolayer biosorption capacities were of 198.9 and 45 mg g^-1, respectively for RR75 and AO51.

Remediation of anionic dye from aqueous system using bio-adsorbent prepared by microwave activation

The present study was attempted to ascertain the possible application of activated carbon as a cost-effective and eco-friendly adsorbent prepared via microwave-assisted chemical activation. The activated carbon was characterized using different techniques. The various adsorption parameters have been optimized to examine the viability of activated carbon as a plausible sorbent for the remediation of Congo red (CR) dye from the aquatic system. The equilibrium data adequately fitted to the Langmuir isotherm with better R² (0.994). The maximum adsorption capacity (q_m) of activated carbon was recorded to be 68.96 mg/g. Additionally, sorptional kinetic data were examined by reaction-based and diffusion-based models such as pseudo-first-order and pseudo-second-order equations, and Elovich, intra-particle diffusion, and Dumwald-Wagner models, respectively. The computed values of thermodynamic parameters such as free energy change (ΔG⁰), enthalpy change (ΔH⁰) and entropy change (ΔS⁰) were recorded as -3.63, 42.47 and 152.07 J/mol K, respectively, at 30°C, which accounted for a favorable, spontaneous and endothermic process. The regeneration study emphasized that the percentage uptake declined from 90.35% to 83.45% after six cycles of testing. So, our findings implied that activated carbon produced from biomass must be cost-effectively used as an adsorbent for detoxifying the CR dye from industrial effluents.

Adsorption of Methylene Blue Dye onto Bush Cane Bark Powder

The adsorption of methylene blue (MB) dye on bush cane bark powder has been studied by analyzing the effect of contact time, initial dye concentration, adsorbent dose, pH, and temperature on the amount of the MB dye adsorbed per unit mass of the bush cane bark powder adsorbent. An optimum adsorption could be achieved during 80 min contact time but, thereafter, decreased with contact time beyond 80 min. The adsorption of the methylene blue dye increased with increasing the initial dye concentration, temperature and pH. However, the amount of methylene blue adsorbed decreased with increasing the dosage of the adsorbent; a phenomenon attributed to a plausible agglomeration of the adsorbent and blocking of the preferred adsorption sites with increasing adsorbent dosage. The adsorption mechanism of the dye obeyed the Freundlich isotherm. Kinetic studies showed that the methylene blue adsorption onto bush cane bark powder adsorbent followed a second order reaction kinetics. The adsorbent was characterized by Fourier transform infra-red spectrophotometer and scanning electron microscope analysis.

Adsorption of U(VI) ions from aqueous solutions by activated carbon prepared from Antep pistachio (Pistacia vera L.) shells

Antep pistachio (Pistacia vera L.) shells an abundant and low cost natural resource in Turkey was used to prepare activated carbon by physiochemical activation and carbon dioxide (CO2) atmosphere as the activating agents at 700°C for 2 h. The adsorption equilibrium of U(VI) from aqueous solutions on such carbon has been studied using a batch system. The parameters that affect the U(VI) adsorption, such as particle size of adsorbent, contact time, of pH of the solution, and temperature, have been investigated and conditions have also been optimized. The equilibrium data for U(VI) ions’ adsorption onto activated carbon well fitted to the Langmuir equation, with a maximum monolayer adsorption capacity of 8.68 mg/g, The Freundlich and Dubinin–Radushkevich (D–R) isotherms have been applied and the data correlated well with Freundlich model and that the adsorption is physical in nature (Ea =15.46 kJ/mol). Thermodynamic parameters [ΔHs =11.33 kJ/mol, ΔS=0.084 kJ/molK, ΔG (293.15 K)=−13.29 kJ/mol] showed the endothermic heat of adsorption and the feasibility of the process.